title: Isothiocyanates reduce mercury accumulation via an Nrf2-dependent mechanism during exposure of mice to methylmercury.
abstract: BACKGROUND
  Methylmercury (MeHg) exhibits neurotoxicity through accumulation in the brain. The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) plays an important role in reducing the cellular accumulation of MeHg.
  
  
  OBJECTIVE
  We investigated the protective effect of isothiocyanates, which are known to activate Nrf2, on the accumulation of mercury after exposure to MeHg in vitro and in vivo.
  
  
  METHODS
  We used primary mouse hepatocytes in in vitro experiments and mice as an in vivo model. We used Western blotting, luciferase assays, atomic absorption spectrometry assays, and MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assays, and we identified toxicity in mice based on hind-limb flaccidity and mortality.
  
  
  RESULTS
  The isothiocyanates 6-methylsulfinylhexyl isothiocyanate (6-HITC) and sulforaphane (SFN) activated Nrf2 and up-regulated downstream proteins associated with MeHg excretion, such as glutamate-cysteine ligase, glutathione S-transferase, and multidrug resistance-associated protein, in primary mouse hepatocytes. Under these conditions, intracellular glutathione levels increased in wild-type but not Nrf2-deficient primary mouse hepatocytes. Pretreatment with 6-HITC and SFN before MeHg exposure suppressed cellular accumulation of mercury and cytotoxicity in wild-type but not Nrf2-deficient primary mouse hepatocytes. In comparison, in vivo administration of MeHg to Nrf2-deficient mice resulted in increased sensitivity to mercury concomitant with an increase in mercury accumulation in the brain and liver. Injection of SFN before administration of MeHg resulted in a decrease in mercury accumulation in the brain and liver of wild-type, but not Nrf2-deficient, mice.
  
  
  CONCLUSIONS
  Through activation of Nrf2, 6-HITC and SFN can suppress mercury accumulation and intoxication caused by MeHg intake.
authors.affiliation: Doctoral Programs in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Toyama
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Shinkai
authors.forename: Akira
authors.initials: A
authors.lastname: Yasutake
authors.forename: Koji
authors.initials: K
authors.lastname: Uchida
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Kumagai
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D017879:Isothiocyanates / Q000494:pharmacology*; D008297:Male; D008628:Mercury / Q000378:metabolism*; D008767:Methylmercury Compounds / Q000378:metabolism / Q000633:toxicity*; D051379:Mice; D008817:Mice, Mutant Strains; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D013454:Sulfoxides; D013861:Thiocyanates / Q000494:pharmacology
chemical_list: C111984:6-methylsulfinylhexyl isothiocyanate; D017879:Isothiocyanates; D008767:Methylmercury Compounds; D051267:NF-E2-Related Factor 2; D013454:Sulfoxides; D013861:Thiocyanates; D008628:Mercury; C016766:sulforaphane